Method and apparatus for mixing



An 12, 1958 M. M. BEAN 2,846,726

METHOD AND APPARATUS FOR MIXING Original Filed Dec. 2, 1953 2Sheets-Sheet 1 Fig.1

INVENTOR Mar/Ls M. Beam 660L224, mm 1 J ATTORNEYS Aug. K2, l958 M. M.BEAN 2,846,726

METHOD AND APPARATUS FOR MIXING Original Filed Dec. 2, 1953 2Sheets-Sheet 2 Z4- 22 f 28 /4 i 36 Fig. 2

lNVENTOR, Mom/s /1 Bean BY (M224 Mama AJ' ATTOR N E Y5 United StatesPatent METHOD AND APPARATUS FOR NHXJNG Morris M. Bean, Yellow Springs,0hio, assignor to Morris Bean and Company, Yellow Springs, 0hio,.acorporation of Ohio Original application December 2, 1953, Serial No.395,737. Divided and this application May. 28, 1957, Serial No. 666,500

2 Claims. (Cl. 1847.5)

This invention relates to apparatus for. thoroughly mixing dry andliquidmaterials .to form a soft, smooth mix, .and for delivering .theresulting-mix through a convenient conduit. More particularly, theinvention relates to. theseparation and injection of slurries ofsettabl'e materials such as. plaster of Paris-and the like.

.In. the preparation of such mixtures,..difiiculty has beenexperienced'inso blending dry and wet constituents. as to insureasmooth, uniform mixture freefrom air bubbles. Another difliculty is toreach such smooth uniform con-. sistency before the binder has setup andthereafter to expel the mix from the apparatus before it has set. Wherethis. problem has been met by using a slow setting mix to give time forthe mixing operation plus necessary holding intransit before it ismolded, production .hasbeen unduly delayed with serious increase in thecapital tied up in. mold equipment (mold is. used broadly herein toinclude patterns, etc. as. well as external molds).

The present invention aims to provide improved apparatus for effecting athorough mixing of dry and wet constituents into a slurry and .holding,the slurry ready for molding. during the variable delays normallyencountered. in manufacturing and yet to supply the mix on demandincondition for prompt. setting up in a mold;

An.important feature of the'invention is the simple mixing devicewhichnot only effects the mixing of the dry and. wet. constituents of theslurry, but. also: subjects the solid particles of, the slurry 'toarubbing. andsqueezing operation, This results both in: improving theuniformity of the mixture and" at the same time in drivingout any gases.

7 Another important feature of .the .invention is the novelejectionmeans and. its arrangement. in the apparatus.

It.is important also that ,alliparts which contact the mix are so simpleand accessible that; an efiective washing, of all operating parts canbeeffected by a simple flushing operation.

Further important features are. themaintenance of a controlled headon-xthe slurry'andautomatic supply of materialsto replace: mixwithdrawn: from: the machine;

A novel construction of the ejector, particularly of the ejector piston;and the use of the. ejector piston asa valve, are also. important;features;

Another important feature iS thal'S-th'CYCIlDgf of the appurtenant partsbeing shown diagrammatically, certain parts in phantom and part. of theheat exchanger "b 3 broken away:

Figure 2 is a view, on enlarged scale, mainly invertical section butpartly in elevation, of the-mixing ehams ber-and mixing mechanismtogether with the-ejection pump connected therewith;

Figure 3 is a similarly enlarged sectional detail showing the ejectorpiston at the lower end of its stroke and with its expansible glandcontacting the cylinder wall to prevent by-passing of the slurryaround'the piston;

Figure 4 is a sectional view of a modification-in which a fixed ringgear engages pinions on the severalroller shafts to positivelydetermine-the rotation sp'eed ofthe mixing rollers;

Figure 5 is' a fragmentary cross-sectionalview similar to Figure 3showing a modified expansiblepiston.

In the embodiment of the invention'her'ein illustrated, asuitable frame8'is provided for supporting the operating parts of-the mechanism.Advantageou'sly, tlrisis a conventional type with an upright pillarmounted'on a base provided with casters for full mobility.- In the'drawings .as here shown, thi'sframe 8 ispartially'broken away for clearshowing of the operating parts.

' Thedevice embodying my invention comprises a mixing chamber 2, inwhich the constituents of a slurry to be formed are mixed, andmixin'g'means 10 operating in said mixing chamber to crush and' rub theconstituents of the slurry against the chamber wall. In this emBodi-Jment, mixingv chamber 2 is shown-asa casting carried by abracket 6 ofthe frame 8. The mixing chamber is funnel-shaped withthe bottom part 11of-its walls-' 'at"a greater angle to its axisthan-alo'n'g their majordepth.-

The rollers 10- are mounted inibearingsin a yoke "12' which has a hub 14rotated inbearing 16 supporte'd'on bracketZO; This is also attached tothe vertical frame member 8. The belt 22 drives the hub 141f-rompulley24 on a gearreducer 26 driven by a motor 282- Asshown, the bearings foreach of the rollers 10 are eccentrically mounted in a. cylinder 36fitted in the yoke: 12. These cylinders can be rotated by a-tooiinserted in one of a plurality of holes 38 :and thus the rollers '10 canbe adjusted radially to bring them into the desired tangential. contactwith-the inner; surface of the mixing chamber 2. Each cylinder 36 can belocked in ad' through the spraynring, 46 and pipez48. Theproport-ior'ring of these materialsis advantageously'eifect'ed auto?matically by apparatus such as that disclosed in said: Patent No.2,574,238. However, in order toxavoid re peat-lug here the extensivedescription and drawings of" thepropoitioning.apparatus as given: in mypatenu l have shown. diagrammatically, in Figure l,.-an"ordinary"proportioning feeder 49-WhiCh. measures "out the powderfeed inresponse-to: or in conjunction withifiow-of the liquid, theliquid, in turn or conjointly, being c'ontrolle by a relay andsolenoid-valve, .from the'f'eeler circuitfi eluding: probe: 52.. As thelevel of the. slurry in chamber 2 rises to. that shown at'50, electricprobe--52 completes a circuit to actuate a solenoid valve controllingthe flow of;

liquid; and,. with. the flow of. liquidrstoppeiino further.proportioning; device until? dry material. can be fed by the theliquidflow isre-established.

If'the proportioning. feed of. PatentNo.-2,57-4;23'8 lis used, theapparatus of Figure 1, except tor'49'istusedwitii the apparatus of thepatent above the. -.Wet-coreunih127.

The chute 59 of. thepatentthenbecomes chute 44 'ofis the apparatusherein set forth. and. the water supply-pipes:

72 of the patent and distributor 74 become pipe 48 and distributor 46above described. The feeding and proportioning apparatus of Figures l-7,9l2 and 21, as well as the mounting and delivery means of Figures 22-29,can be used substantially as shown in said patent. This combination thenwould operate as follows:

As the level of the slurry in chamber 2 rises to that shown at 50,electric probe 52 energizes a relay which in turn energizes the timer,which shuts off a motor for a definite time interval allowing the slurrylevel 50 to drop a short distance, dependin upon the rate of dischargefrom nozzle 161. This motor drives the plaster meter wheel and the watermeter pump geared together to maintain a uniform consistency, and at theexpiration of the time interval the motor turns on and the liquid levelapproaches the electric probe 52.

This mixing chamber as above described makes possible the satisfactoryoperation at maximum demand, thus requiring very little storage of themixed material, which would have to be wasted when the production wasinterrupted for more than a few minutes.

The cylindrical rollers 10 travelling over the conical surface lagbehind said surface at the top and turn faster than a rolling speed atthe bottom. Thus, a rubbing and smearing action highly effective formixing the powder into the liquid is achieved. The drag forward on thetop of each roller is balanced against the drag back on the bottom ofthe roller. Only a section near the center of the roller actually rollson the conical surface of the chamber without slippage. The conical endsof the rollers extending to and even over the outlet from the mixingchamber and rotating at relatively high speed, create a final turbulencein the exit and assure that all material before leaving the mixingchamber will have been rubbed between the rollers and the chamber wall.

The discharge end of the mixing chamber 2 merges into a cylinder 54provided with an ejector piston 70. The cylinder 54 is secured by aclamping ring 59 bolted over flange 56 and onto the bottom of thechamber 2.

A coupling 66 shown, also in Figure 2, connects the cylinder 54 to thedischarge line, including pipes 68, 148 and 160. The inside of thiscoupling is smooth for streamline flow and is contoured similar to thebottom 78 of piston 70 (see Figure 3).

The probe 69 extending down from piston 70 aids in keeping pipe 68 open.

The piston 70 comprises essentially a gland, here shown as a ring 71 ofrubber-like material, advantageously a thick-walled tube of pure gumvulcanized rubber or any elastomer composition sufliciently hard andstrong and tough to resist the high fluid pressures encountered 'and therepeated extrusion and retraction from, and between flange 74 and nut78. In the modified piston shown in Figure 3, a toroidal ring 71a likean automobile tire is used, with its inner rims clamped respectively tothe flange 74a and the nut 78a. In either case, when the gland issqueezed, it extrudes laterally into the shape shown in Figure 3. Whenthe flange 74 and nut 78 are moved apart, the gland is extendedlongitudinally and retracted radially to the shape shown in Figure 2, inwhich the slurry may by-pass the piston. As shown in greater detail inFigure 3, lateral extrusion and retraction of the piston are effected bythe relative movement of the hollow rod 72 and the center rod 76.

Instead of mechanically expanding the piston ring 71, as shown inFigures 2 and 3, this function can be performed pneumatically orhydraulically, e. -g., by using for ring 71b an inflatable annular tubeas shown in Figure 5 with an opening at 79 connecting it through thebore of tubular rod 72b, to the hose 140]). The ring 71b is cemented tothe rim of flange member 74b, particularly around the hole 79.

Great care must be exercised in design of piston 70 to keep fromintroducing air between 70 and 71, or to prevent leaks around tube 71aor 71b.

Rod 72 is also flanged at its upper end and rigidly connected to thebottom of the cylinder 82, and rod 76 is connected to piston 80 in thecylinder 82, so that fluid pressure in the cylinder compresses andextrudes ring 71. A spring 84 in this cylinder urges piston 80 and rod76 downward relative to rod 72, to retract ring 71 to the form shown inFigure 2.

The cylinder 82 is moved bodily by the piston rod 86 driven by piston 88in cylinder 90 counted on bracket 92 of frame 8. Rod 86 is threaded foradjustment and provided with lock nuts, to control the amount of squeezeon piston ring 71 so as to assure a tight fit in cylinder 54 withoutexcessive friction.

A three way solenoid valve 98 operates to introduce air pressure intothe cylinder 82 to extrude ring 71 when its solenoid is energized and tovent air from the cylinder to retract the gland when the solenoid isreleased.

A four-way solenoid valve 102 introduces air pressure above piston 88and vents the space below the piston when its solenoid is energized,thus urging piston 70 down into cylinder 54 and imposing a suitable headon the slurry for delivery from the apparatus; when the solenoid isreleased, valve 102 vents the top and introduces pressure below thepiston 88 to lift piston 70. A limit switch 106, normally closed andhaving one contact positioned to be engaged by finger 108 on cylinder82, limits the injection stroke of the piston 70 by breaking theenergizing circuit of valve 102.

A controlling switch 116 as shown may be put into any of threepositions: run, OE, and start. When it is in the start or the runposition, it energizes the motor 28, e. g. by conventional circuitconnections (not shown).

In the start position this switch makes connections around the relay123, i. e., the circuit of valve 98 is closed independently of the timer112; whereas in the run position, the switch connects both solenoidvalves 102 and 98 through contacts 126 and 128 of relay 123 thus makingthem subject to control by the timer. If this switch 116 were left inthe start position, the piston 70 would not be etfectively retracted,but would serve only as a stopper. If the switch 116 were left always inthe run position, it would not operate valve 98 until relay 123 hadreceived a pulse from the timer; and then pumping would start. The startposition of switch 116 provides for operation of fluid motor 80-82 tostopper chamber 2 before the timer 112 is started.

An electronic (or other available) pulse timer 112, operated from thefeed line through the wires 114 and 118 and the hand operated switch122, closes the circuit to the relays 123 for short pulses at timeintervals predetermined by the setting of the timer. Contacts 126 and128 are provided on relay 123 to be closed by its armature; and theconnections 130, 132 and the normally closed limit switch 106 provide aholding circuit for the winding of the relay so that, once closed, itremains closed through this holding circuit until switch 106 is opened.Once opened, the relay remains open until a pulse from the timer 112re-energizes it.

Contact 126 closes the above mentioned holding circuit for relay 123 andthe contact 128 closes circuits to the solenoid valves 98 and 102. Atfirst, the energizing circuit for relay 123 is through the connection124, timer 112, contacts 122; but when relay 123 is operated the circuitis through connection 130, limit switch 106 and connection 132.

Air-flow control valves are provided at 134 and 136 to regulate thespeed of piston 88 and ejector piston 70 connected to it. An air controlvalve 138 similarly regulates the speed at which the ejector piston 70is expanded or contracted by movement of piston 80. Air line 140 is aflexible hose or pipe to accommodate vertical movement of the cylinder82.

In Figure 4 of the drawings is shown a modification of the embodimentshown in Figures 1 to 3 wherein the rollers a are positively rotated bybevel gears 141 which mesh with the fixed ring gear 142'mounted onbracket a so that the rotation of the yoke lz'drives the pinion 141 overthe ring gear 142 and thus rotates each of therollers 10a. The ringmaybe external or internal. By the proportioning selected for therespective diameters of the pinion gears 141 and the, ring gear 142,any, desired speed of rotation may be given to the. rollers 10a and anydesired rubbing action attained.

In the operation of this mechanism, switch 116 is moved to its startposition, whereupon the motor 28 is started and solenoid valve 98 isenergized to cause the expansion of the injector piston 70. This closesthe outlet from the mixing chamber 2.

The liquid and dry materials to be mixed are then introduced by theautomatic proportioning device 49 and through the conduit 44 and a sprayhead 46 respectively. The cylindrical rollers 10 meanwhile have beenstarted in rotation by motor 28, driving through belts 22. The rollersoperate against the inner surface of the mixing chamber 2 with both arolling action to squeeze out any air bubbles, a crushing action tobreak up any lumps'of the powder, and a rubbing action against the innersurface of the chamber to thoroughly wet the surface of every particleand produce uniform slurry. By reason of the fact that the upper ends ofthe roller 10 travel around the longer circumference of the top of thefunnelshaped chamber 2 while their lower ends traverse a shorter path atthe bottom of the chamber, the rubbing action varies both in directionand degree. The frustoconical end 144 of the rollers 10 and the fittingconical bottom 11 of the chamber permits the rolling, rubbing andcrushing action to extend substantially to the outlet of the chamber 2and thus prevents settling out of solids and retards solidification ofthe slurry when the discharge is shut off.

The introduction of liquid and dry constituents and the mixing continueuntil the material fills the chamber 2 to the level 50, when it contactsthe electrical probe 52 to stop further introduction of theconstituents.

When the chamber 2 is thus filled, the switch 116 is moved from startposition to run position and the switch 122 is closed to start the timer112. Removing the switch 116 to the run position releases the solenoidvalve 98 permitting exhaust from the cylinder 82 to allow the piston 80to return and retract the gland 71. As timer 112 moves, it soon sends apulse to the relay 123. After each pulse, the relay 123 is heldenergized by the holding circuit through contacts 126, connections 130,132 and limit switch 106 until limit switch 106 is opened. With contacts128 closed, both valves 98 and 102 are operated so that piston 80 ismoved up, expanding piston 70 to a tight fit in cylinder 54, and piston88 is driven down causing piston 70 to move down and eject the slurryfrom cylinder 54 through the line 68, 148 and 160.

At the end of this stroke, a projection 108 on cylinder 82 strikes andopens limit switch 106, which drops relay 123; and solenoids 98 and 102are thus de-energized which reverses both solenoid valves to retract thepiston gland 71 and lift the piston 70.

The liquid supplied through the pipe 48 and spray head 46 isadvantageously cold enough to substantially retard the setting of theslurry. In the case of plaster of Paris, I thus use water at atemperature about 0 to 20 C. To the same end, the chamber 10 and/orcylinder 54 may be jacketed or provided with a cooling coil and arefrigerant fluid circulated to chill the mix to that range. It isdesirable, however, that the slurry set rapidly when it has beenintroduced into the mold. In the illustrative embodiment of theinvention, therefore, a heater 146 is provided so that the slurry isdelivered from the discharged nozzle into the mold in a condition readyfor quick setting, advantageously 50-65 C. The required temperature isautomatically maintained by supplying to a steam jacket 146 saturatedsteam at a pressure corresponding to a slightly higher temperature, e.g., of a pressure about 2 to 30 p. s. i. above atmospheric. Thecondensate drains from the low point of this jacket through a pipe 152:and a thermostatic trap 154 and the discharge pipe 156. A steam gauge158 shows the pressure and/or temperature. A shut-off valve 150 providesfor stopping the heat or reducing the rate ofheating, if the dischargeis to be cut off "for any substantial time or unduly retarded.

A flexible tube 160 provided with a nozzle 161 receives the slurry fromthe tube 148 and enables the operator to deliver it at the desiredpoints in the molds, etc.

The slurry is delivered from the nozzle 161 at a temperature near thatof its maximum setting speed and in a stream of about A to /2 diameteror larger, (the particular nozzle being chosen to give the mostadvantageous size stream for filling the plaster into the detail of theparticular mold). The velocity of the stream, which is regulated by theair pressure supplied through the valve 102, is adapted to drive theplaster into the detail by its momentum but without whipping it up so asto entrain any air. Thus, in one preferred embodiment the air suppliedby the piston .keeps a head of lbs. per square inch on the slurry.

As one example: A dry mix containing 42% gypsum cement, 47% fine sand,8% talc and 3% terra alba was mixed with water at 5 C. to theconsistency of soft mud or slurry. This could be held safely in themachine for four minutes and it would take about 15 minutes thereafterto set. The chamber 2 was, therefore, designed to hold only enough ofthe mix for about a two-minute supply for normal use. After this mix hadbeen pumped through the heater 146, its temperature was raised to 50 C.and the mix was then set in 2.8 minutes, thus allowing adequate time forfilling it into the mold and for it to flow and form itself into thedetail of the mold.

As above pointed out, one of the great advantages of this invention isthat slurries such as gypsum plaster can be made and a supply kept at atemperature so low that setting will not occur in the machine and yetwill occur promptly after delivery. Because the piston and the mixingdevice are immersed in the slurry throughout the operation of theapparatus and operate through the open upper surface of the material inthe hopper without glands or other devices which could leak air belowthe surface of the slurry, the danger of introducing air bubbles issubstantially entirely eliminated and the mechanical design of theapparatus is greatly simplified by the avoidance of the need forstufling boxes or glands to control such air leakage into the apparatus.

When use of the apparatus is to be discontinued, the feed is cut off andpumping continued until the hopper is substantially emptied.

Water for flushing out the apparatus is run in at 166. This serves towash out the mixing hopper 2 and to clean the rollers 10 and piston 70and all parts with which the slurry has been in contact. By leaving theapparatus running while the flushing water is running in and through theapparatus, pump 70 and rollers 10 serve to agitate the water and to giveit relatively high velocity along the surfaces which need to be washedand thus facilitate the cleaning of all parts which have been covered bythe plaster. Rod 69 also helps in assuring a thorough washing of thepipe 68.

I claim:

1. The process of preparing a settable and moldable slurry including awater-setting constituent, such as gypsum plaster, which consists inmixing the theretofore dry constituents of the slurry with water,chilling the slurry to a temperature sufficiently below atmospheric tostrongly retard the setting of the slurry, rubbing and squeezing thewetter solid particles of the slurry during the mixing until occludedgases have been substantially completely expelled while retaining thetemperature of 7 the slurry substantially below atmospheric, thenejecting the slurry under pressure into a form with heating of theslurry as it is discharged.

2. The process as defined in claim 19 wherein the amount of slurry beingmixed at any time is substantially less than that consumed at thecurrent rate of use within the setting time of the slurry at said lowtemperature;

References Cited in the file of this patent UNITED STATES PATENTS LakeMay 6, 1924 Edwards Aug. 1, 1933 UNITED STATES PATENT ()FFICECERTIFICATE OF CORRECTION Patent No, 2, 846, 726

August 12, 1958 Morris Mo Bean Column 6 line '73, for "wetter" for thread m Wetted m e claim reference numer column 7, lina 4, al "19" read m1 o Signed and sealed this 23rd day of Decembevr 1958..

SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Oflicer Commissiongr ofPatents

